Recently, in mobile communication apparatuses such as cellular phones and so on, a variety of filter circuits have been used in order to obtain desired frequency characteristics. Further, cellular phones are strongly required to be reduced in size. As such, various types of piezoelectric filters including surface acoustic wave filters are widely used as the components that configure the above-mentioned filter circuits. For example, Japanese Unexamined Patent Application Publication No. 2003-51731 cited below discloses a filter device that is configured with a surface acoustic wave filter.
With regard to this type of filter device, a method in which an LC chip is externally connected so as to widen a band width of a band-pass filter that is configured with a piezoelectric filter such as a surface acoustic wave filter or the like has been known.